1. Field of the Invention
The invention relates to a jack whose rod can be actuated with a translational movement or a rotational movement or with a combination of these two movements.
2. Description of the Prior Art
Hydraulic, pneumatic and oleopneumatic jacks and generally jacks with a piston and a pressurizing agent as well as electrical jacks are well known. They include a rod which is mounted in a cylinder and which is driven in translation with respect to the latter. In jacks with a pressurizing agent, the rod is fast to a piston which slides in fluid-tight manner in the cylinder whilst intake and exhaust passages for said agent are formed in the two ends of the cylinder so that the piston can be driven with a translational movement called "rise and fall".
However it is often necessary, in the field or automation for example, to have jacks available whose rod is capable of being actuated in addition to its conventional rise and fall movement, with a rotational movement, so that, for example, an arm fixed to the end of the rod benefits from these two movements if necessary combined.
This is why a jack has been conceived which is provided with a cylinder and a piston, both having a curvilinear triangular section so that they are fast in rotation whilst the cylinder is rotatably mounted in a support in such a way that it is possible, by means of a suitable device, to rotate the cylinder at will and through this fact, the rod which is fast to the piston.
This device has numerous drawbacks. Firstly, its cost price is particularly high, given principally the difficulty of producing a bore of curvilinear triangular cross-section. In addition, a great disadvantage resides in the fact that the machining of the cylinder is limited. In fact, apparatus capable of producing bores of this type is not only onerous, but has technological limitations as to length, which restricts the possibilities since the travel of the rod depends obviously on the length of the cylinder.